But what's this? A royal blue cork? A purple cork? A bright orange cork?

These and other startling stoppers are being impaled on more and more corkscrews these days. In fact, the lowly, long-neglected cork is now the unlikely object of startled comments at restaurants and of an out-and-out international bottle brawl in the rarefied realm of wine aficionados and vintners.

In the tradition-bound world of wine, the growing use of plastic corks--some with shocking colors--is riling up debates as fierce as disputes about the merits of California versus French wines. Synthetic corks are being used by more winemakers, especially in California and Australia, to get around a persistent spoilage problem caused by contaminated corks.

For many wine lovers, who assign nearly mystic importance to the smallest details of bottling, storing and serving the fermented fruit of the vine, the notion that a chunk of plastic--a lowly blob of curdled petroleum--might sully their beloved merlots and chardonnays is enough to make them chug a jug wine.

Inevitably the sight of a plastic cork raises questions about the quality of the wine. If the cork is plastic, can the vin be anything but ordinaire?

"When they see a plastic cork, it often does initiate a little dialogue," said Karen King, wine director at New York's Union Square Cafe, which serves California and Oregon wines with synthetic stoppers. "It's kind of an unexpected twist. We are very attached to the ceremony of the cork, and we don't want anything about that ceremony to change."

The row has taken on the tit-for-tat contours of recent spats about paper versus plastic grocery bags, or disposable versus cloth diapers. For every tiny fact trotted out by the "synthetic closure" forces, cork loyalists pop back with an answering salvo.

Although the debate is fairly recent, the cause reaches back more than 300 years. According to wine lore, the Benedictine monk Dom Perignon, who perfected the technique for putting bubbles in Champagne, introduced the use of cork in wine bottles in the late 17th Century.

Ever since, wine experts have been resigned to being disappointed when they open some bottles of even the best-pedigreed wines and discover that the contents have the odor of "wet paperbacks in a basement after a flood." That is how Christine Blumer, director of special events at Sam's Wine and Spirits on Chicago's North Side, described the phenomenon known as "corked wine."

This musty odor usually carries over to the wine itself, making it virtually undrinkable. As much as 8 percent of all wine ends up being sluiced down a drain because of corkiness.

The source of the problem is a cork fungus that produces a dank-smelling chemical so potent that quantities are measured in parts per trillion. One half-tablespoon would ruin all the wine that America produces in a year.

"You can't tell from looking at the cork before you put it in that it is infected," said Dave Read, wine department manager at Sam's. "And it doesn't just affect cheap wine. I've talked to people who have had it happen to $700 bottles of wine."

Europeans vintners have long taken a typically Continental attitude to corked wine, shrugging that nothing could be done.

But cost-conscious producers in America and other newer wine-growing regions, such as Australia, are eager to reduce losses from corked wine, as are large supermarket chains in Britain. Most restaurants and wine merchants will replace the wine or give a refund, but even so, the experience can sour a customer for the future.

"People are a lot less understanding of a $150 bottle of Bordeaux being corked than they are of a $5 bottle of Spanish wine," Read said. "I would say it's the biggest problem facing the wine industry right now."

Plastic corks seemed to be the answer. The biggest maker, Supreme Corq of Kent, Wash., produces plastic plugs that have the tan color and dark streaking found in real cork. They also produce corks that are banana yellow, royal blue, forest green and bright orange.

More than 100 million bottles at 230 wineries around the world have been sealed with the company's plastic corks, which are made from the same compound used to make heart valves. The product has so much promise that it attracted Microsoft Chairman Bill Gates as an investor.

"It's more consistent from bottle to bottle," said Marla Rosenberg, Supreme's vice president for sales. "Natural cork is a natural product, so there's no guarantee of consistency. Cork can break when you remove it. Cork can leak."